The present invention relates to a stent-graft-membrane for placement at a treatment site within a body vessel or organ to enhance and direct fluid flow therethrough and a method of making the same. More particularly, the invention relates to an implantable endoprosthesis such as a stent combined with a generally impermeable membrane layer and a permeable graft layer. The graft and the membrane provide biocompatibility with tissue at the treatment site and provide biocompatibility with fluid in the lumen.
Intraluminal implantable endoprostheses such as self expanding stents, grafts and stent-grafts are known and are, for example, shown in U.S. Pat. Nos. B1 4,954,126; 5,116,360; 5,133,742; 5,591,226; 5,653,747; and 5,679,470. A covered stent is described in International Publication Number WO 94/24961. A polyurethane is described in U.S. Pat. No. 4,810,749. A porous implantable material is described in U.S. Pat. No. 4,475,972. A method of forming an implantable graft is described in U.S. Pat. No. 4,738,740.
U.S. Pat. No. B1 4,655,771, entitled, Prosthesis Comprising Expansible or Contractile Tubular Body, discloses a prosthesis comprising a flexible tubular body for tansluminal implantation.
U.S. Pat. No. 5,061,275, entitled, Self-Expanding Prosthesis, discloses a resilient, elastic self-expanding prosthesis comprising a flexible tubular body.
U.S. Pat. No. 5,645,559, entitled, Multiple Layer Stent, discloses a radially self-expanding stent having multiple layers that includes a medial region and proximal and distal cuffs having diameters greater than the medial region diameter when the stent is in the relaxed state. A silicone coating circumscribes at least the medial region of the stent.
U.S. Pat. No. 5,718,159, entitled, Process for Manufacturing Three-Dimensional Braided Covered Stent, discloses a prosthesis having a flexible tubular three-dimensionally braided structure of metal or polymeric non-filaments, and polymeric multifilament yarns.
U.S. Pat. No. 5,741,333, entitled, Self-Expanding Stent For A Medical-Device To Be Introduced Into A Cavity Of A Body, discloses a self-expanding stent.
U.S. Pat. No. 5,755,774, entitled, Bistable Luminal Graft Endoprosthesis, discloses a luminal graft endoprosthesis or endovascular graft which is capable of dilation and support functions and suitable for the endoluminal repair of vascular lesions and the like. An expandable support or stent is combined with a tubular graft made of a material having two unstressed conditions to provide a combined stent-graft wherein the graft material is secured to either or both of the internal or external surfaces of the stent.
U.S. Pat. No. 5,534,287, entitled, Methods for Applying an Elastic Coating Layer on Stents, discloses a coated stent comprising a cylindrical wall formed by meshed wires and a covering layer of elastic material extending on a portion of its length, with an outer surface, and totally embracing the wire mesh.
U.S. Pat. No. 4,850,999, entitled, Flexible Hollow Organ, discloses a flexible hollow organ, especially a vascular prosthesis intended for implantation in the human or animal body parts. The hollow organ includes a flexible prosthetic tube serving for a throughflow of a medium or which consists of such a prosthetic tube. A wall of the prosthetic tube exhibits at least one braided hose of flexible, elastic threads produced as a hollow meshwork.
A stent-graft is described in U.S. patent application Ser. No. 08/640,253, entitled xe2x80x9cCobalt-Chromium-Molybdenum Alloy Stent and Stent Graftxe2x80x9d, filed Apr. 30, 1996.
A stent-graft is described in U.S. patent application Ser. No. 08/993,985, entitled, Stent-Graft with Bioabsorbable Structural Support, filed Dec. 18, 1997.
A stent-graft is described in U.S. patent application Ser. No. 08/946,906 entitled, Stent-Graft with Braided Polymeric Sleeve, filed Oct. 8, 1997.
All references cited herein are incorporated herein by reference in their entireties for all purposes.
The stent-graft-membrane of the present invention has at least three layers and is intended for treatment of vascular lumens, non-vascular lumens or organs in the body. The three lavers include a structural stent laver a raft laver and a membrane laver. The three layers may be formed in different combinations of layers. A need exists for a stent-graft-membrane of the present invention having layers with surfaces that are selected to be biocompatible with the tissue or fluid for which they are associated with while treating vessels or organs. Biocompatibility means that the implant is accepted by the host tissue and does not create an adverse biological response.
The stent-graft-membrane may advantageously be used in a variety of medical applications including intravascular treatment of stenoses, aneurysms or fistulas; maintaining openings in the urinary, biliary, tracheobronchial, esophageal, renal tracts, vena cava filters; repairing abdominal aortic aneurysms; or repairing or shunting damaged or diseased organs.
In sum, the invention relates to an implantable endoprosthesis including a first number of elongated members wound helically in a first common direction and crossing a second number of elongated members wound helically in a second common direction. The crossing of the first and second elongated members define an angle and form a generally tubular body having an inside surface, outside surface, ends and a middle portion. The first and second elongated members are braided in a braid pattern and are configured to be constrainable to a reduced diameter and self-expandable to an increased diameter. The tubular body is disposed at a treatment site in a body vessel or organ having body tissue. A passage extends in a longitudinal direction at least partially through the generally tubular body. The passage at least partially contains a fluid in the lumen and directs flow. One or more outside layers are disposed over or on at least a portion of the outside surface of the tubular body. An outermost layer of the one or more outside layers is biocompatible with the body tissue. One or more inside layers are disposed over or on at least a portion of the inside surface of the tubular body. An innermost layer of the one or more inside layers is biocompatible with the fluid in the passage. At least one of the one or more outside layers or the one or more inside layers are substantially impermeable to fluids. The inside layer or the outside layer may each include one or more layers. The one or more inside and outside layers may include one or more membrane layers having an average permeability ranging from about 0 cc/cm2/min. to about 100 cc/cm2/min. and/or one or more graft layers having an average permeability ranging from about 50 cc/cm2/min. to about 5000 cc/cm2/min. The outside layer may be a film or membrane made of silicone or polycarbonate urethane and the inside layer may be a graft made of braided PET. The inside layer may be ePTFE or PTFE. The implantable endoprosthesis may be designed to provide structural structural support to a body vessel for a period of time and substantially separate a first body fluid located outside the endoprosthesis from a second body fluid located in the passage. The implantable endoprosthesis may be disposed at a Transjugular Intrahepatic Portosystemic Shunt (TIPS) treatment site. At a TIPS treatment site, the first fluid may include bile and the second fluid may include blood. The braided implantable endoprosthesis may include an opening defined by each end of the generally tubular body. The tubular body may be made of metal, plastic, bioabsorbable or other synthetic or natural materials. The tubular body may have a braid angle or filament crossing angle of between about 65 degrees and 155 degrees.
The invention also relates to an implantable endoprosthesis including a first set of filaments each of which extends in a configuration along a center line and having a first common direction of winding. A second set of filaments each extends in a configuration along a center line and having a second common direction of winding. The first and second filaments form a stent. One or more membrane layers having a first average permeability are disposed over or on at least one of an inside, interstices, or outside surface of the stent or a graft. One or more graft layers having a second average permeability are disposed over or on at least an inside, interstices, or outside surface of the stent. The first and second set of filaments, and the one or more membrane layers and graft layers form a self expanding structure having one or more layers including an inside layer, middle layer, outside layer, embedded layers or combinations thereof, inside surface, outside surface, proximal end, distal end, and a lumen. The inside surface is selected or configured to be substantially biocompatible with a fluid flow through the body lumen and the outside surface is selected or configured to be substantially biocompatible with a body tissue. The first average permeability may be less than the second average permeability. The one or more membrane layers may have an average permeability ranging from about 0 cc/cm2/min. to about 100 cc/cm2/min., and the one or more graft layers may have an average permeability ranging from about 50 cc/cm2/min. to about 5000 cc/cm2/min. The one or more graft layers may include polyethylene terephthalate (PET), expanded polytetrafluoroethylene (ePTFE), polycarbonate urethane (PCU), polyurethane (PU), or combinations thereof. The one or more membrane layers may include siloxane polymers, polyurethane polymers, polycarbonate urethanes, PTFE, ePTFE, or combinations thereof. The one or more membrane layers may be disposed between the graft and the stent. The one or more graft layers may be disposed between the membrane and the stent. The stent may be disposed between the one or more membrane layers and the one or more graft layers. The layers may be bonded with an adhesive. The stent may be made of poly (alpha-hydroxy acid), PGA, PLA, PLLA, PDLA, polvcaprolactone, polydioxanone, polygluconate, polylactic acid-polyethylene oxide copolymers, modified cellulose, collagen, poly(hydroxybutyrate), polyanhydride, polyphosphoester, poly(amino acids), or combinations thereof. The filaments may include Elgiloy(copyright), stainless steel, nitinol, drawn filled tube (DFT), platinum, tungsten, tantalum, or combinations thereof. The graft layers may include a plurality of interwoven fibers, mono-filaments, multi-filaments, or yarns. The membrane layers may include a film, sheet, or tube. The implantable endoprosthesis may substantially exclude a first fluid located outside the surface of the implantable endoprosthesis from reaching a second fluid located in the lumen. The inside layer may be made of a PET polymer. The outside layer may be made of a silicone elastomer. The silicone elastomer may be a coating. The outside layer may be made of a polymer that is resistant to fluid permeability or resistant to tissue ingrowth.
The invention also relates to a method of making a stent-graft-membrane including: forming a first number of elongated members wound helically in a first common direction and crossing a second number of elongated members wound helically in a second common direction. The crossing of the first and second elongated members define an angle and form a generally tubular body having an inside surface, outside surface, ends and a middle portion. The first and second elongated members are braided in a braid pattern and are designed to be constrainable to a reduced diameter and self-expandable to an increased diameter. The tubular body is adapted to be disposed at a treatment site in at least one of a body vessel or organ having body tissue; forming a passage extending in a longitudinal direction at least partially through the generally tubular body. The passage is adapted to at least partially contain a fluid; forming one or more outside layers on at least a portion of the outside surface of the tubular body. An outermost layer of the outside layers is biocompatible with the body tissue; forming one or more inside layers on at least a portion of the inside surface of the tubular body. An innermost layer of the inside layers is biocompatible with the fluid in the passage. At least one of the outside layers or the inside layers is substantially impermeable to a fluid.
The invention also relates to a method of making a stent-graft-membrane including: braiding bioabsorbable filaments to form a tubular braid. The braid having a braid angle; disposing the braid on a mandrel; annealing the braid for a predetermined time to form an annealed stent; removing the stent from the mandrel, the stent having a filament crossing angle; forming a craft having a an average permeability ranging from about 50 cc/cm2/min. to about 5000 cc/cm2/min. on at least one of an inside or outside surface of the stent; adhering at least a portion of the graft to the stent; and forming a membrane having an average permeability ranging from about 0 cc/cm2/min. to about 100 cc/cm2/min. on at least a portion of the stent. The method of making a stent-graft-membrane may further include prior to the step of adhering, applying a thermoplastic adhesive, curable adhesive, or bioabsorbable polymer adhesive to a surface of the stent or to a surface of the graft.
The invention also relates to an implantable endoprosthesis including a first number of elongated members wound helically in a first common direction and crossing a second number of elongated members wound helically in a second common direction. The crossing of the first and second elongated members define an angle and form a generally tubular body having an inside surface, outside surface, ends and a middle portion therebetween. The first and second elongated members are braided in a braid pattern and are configured to be constrainable to a reduced diameter and self-expandable to an increased diameter. The tubular body is adapted to be disposed at a treatment site in at least one of a body vessel or organ having body tissue. A passage extends in a longitudinal direction at least partially through the tubular body. The passage is adapted to at least partially contain a fluid. One or more outside layers are disposed over at least a portion of the outside surface of the tubular body. At least one of the outside layers is a membrane made of a silicone or a polycarbonate urethane material biocompatible with the body tissue. One or more inside layers are disposed over at least a portion of the inside surface of the tubular body. At least one of the inside layers is a graft made of braided PET material biocompatible with the fluid in the passage. The implantable endoprosthesis is configured such that at least one of the outside layers is substantially impermeable to a fluid and substantially separates a first body fluid located outside the endoprosthesis from a second body fluid located in the passage. A first end portion of the implantable endoprosthesis may be disposed in a portal vein and the other end portion of the implantable endoprosthesis may be disposed in a hepatic vein. A middle portion of the braided implantable endoprosthesis may be disposed in a liver. The first fluid may be bile and the second fluid may be blood.
A preferred use includes placing the stent-graft-membrane through a liver. Transjugular Intrahepatic Portosystemic Shunt (TIPS) is formed by an intrahepatic shunt connection between the portal venous system and the hepatic vein for prophylaxis of variceal bleeding, in the treatment of portal hypertension and its complications. Portal hypertension causes blood flow to be forced backward, causing veins to enlarge, resulting in variceal bleeding. The stent-graft-membrane advantageously acts as a shunt to enable blood to flow through the liver to the hepatic vein. The shunt generally decompresses portal hypertension and allows veins to shrink to normal size, stopping the variceal bleeding.
The invention also relates to a method of using a stent-graft-membrane comprising the steps: identifying a treatment site; determinig the tissue, organ or fluid at the treatment site that the inside surface and the outside surface of the stent-graft-membrane are to be associated with; determining one or more materials for the inside and outside surfaces of the stent-graft-membrane that are substantially biocompatible with the tissue, organ or fluid at the treatment site; providing a stent-graft-membrane. The stent-graft-membrane having a first number of elongated members wound helically in a first common direction and crossing a second number of elongated members wound helically in a second common direction. The crossing of the first and second elongated members defining an angle therebetween and forming a generally tubular body having an inside surface, outside surface, ends and a middle portion therebetween. The first and second elongated members are braided in a braid pattern and are configured to be constrainable to a reduced diameter and self-expandable to an increased diameter. The generally tubular body is adapted to be disposed at a treatment site in at least one of a body vessel or organ having body tissue. A passage extends in a longitudinal direction at least partially through the generally tubular body. The passage is adapted or configured to at least partially contain a fluid. One or more outside layers are disposed over or on at least a portion of the outside of the tubular body. An outermost layer of the one or more outside layers is substantially biocompatible with the body tissue. One or more inside layers are disposed over or on at least a portion of the inside of the tubular body. An innermost layer of the one or more inside layers is substantially biocompatible with the fluid in the passage. At least one of the one or more outside layers or the one or more inside layers are substantially impermeable to fluids; inserting the stent-graft-membrane in a delivery device; inserting the delivery device into a body and delivering the stent-graft-membrane and at least a portion of the delivery device to the treatment site; and deploying the stent-graft-membrane into a position at the treatment site.
In the design of an implantable medical device such as a stent-graft-membrane, it is important that each of the component materials be biocompatible with the host tissue. Thus, an implantible medical device should accomplish its intended functional purpose in the body, and should generally not cause an unfavorable reaction in the tissue with which it interacts.
Biocompatibility requirements may vary for different components of an implantible device. For example, in the case of an implant which is placed in a blood vessel, the inside surface of the implant must be biocompatible with the blood flowing through the lumen. Also, the outside surface of the implant must be biocompatible with the tissue of the blood vessel.
For example, in the case of a TIPS stent-graft-membrane, the general purpose of the stent-graft-membrane is to maintain a shunt for blood flow between the portal and hepatic veins. Each component in the stent-graft-membrane has a function which contributes to the general purpose of the device. In a TIPS application, the functional requirement of the stent is to mechanically hold the liver tissue open to maintain the shunt lumen. The functional requirement of the outer membrane is to prevent any inter-mixing of the bile, which is produced by the liver, into the blood which is flowing through the shunt. Inter-mixing of bile and blood may cause the blood to form thrombus. The functional requirement of the inside graft is to provide an interface with the blood which advantageously improves the blood biocompatibilty of the implant.
The stent, graft, or membrane layers may be substantially individual layers that are at least partially bonded together. Alternatively, the stent-graft-membrane may include a stent embedded in the membrane or the membrane embedded in the stent; the stent embedded in the graft or the graft embedded in the stent; and the membrane embedded in the graft or the graft embedded in the membrane. At least one of the stent, graft, or membrane may be embedded in the other.
Each embodiment of the stent-graft-membrane may include a radiopaque tracer wire to make one or more portions more visible during fluoroscopy. Each embodiment of the stent-graft-membrane may include bare filaments at one or more end portions or middle portions.
Still other objects and advantages of the present invention and methods of construction and use of the same will become readily apparent to those skilled in the art from the following detailed description, wherein only the preferred embodiments are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments and methods of construction and use, and its several details are capable of modification in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.